A fluid relief valve type of device in the hydraulic arts is defined as a control means for pressure relieving a particular closed system under pressure. The need for such devices are manyfold and well recognized in the arts. While the state of the art is well advanced, the various relief valve types of devices sold today have certain similar limitations. For one, relief valves as sold today are characterized as having a very limited range of pressure relief settings, and these generally can operate efficiently within a relatively narrow pressure range defined between their pressure pop-off settings and reseating pressures.
Another characteristic problem with present day relief valves is due to their generally complex internal design, that is, their working parts, which are prone to either mechanical failure and/or plugging, especially when subjected to a corrosive atmosphere. Merely constructing the internals of such valves of anti-corrosive materials will not necessarily solve the problem as valve failure is often caused by raw material or by-product plugging of the valve stem due to their complexity of design, especially those providing for fluid flow through its internal mechanism. The net result is that the system does not relieve itself and goes hydraulic whereby a line is ruptured and raw materials are spilled in the environment and/or wasted to the atmosphere. Or, the valve sticks open and raw materials are by-passed from the system and quite often wasted.
Another problem with prior art relief valves which have been designed for a range of different pressure settings is that quite often such valves can be shut off entirely by virtue of the variable pressure setting means built into such values. Because of its simplicity of design, it can be inexpensively manufactured for use in certain conventional operations which have been plagued with relief valve problems, quite often ignored on the basis of being economically unsolvable. With the advent of ecological concern for the environment as well as the need for avoiding waste of natural resources, the present valve mechanism finds particular application in such areas as fluid transporting operations, for example, pumping fluids between vessels at any pressure.
By way of specific example, in the pumping of fluids aboard vessels, ships, barges, etc., the U.S. Coast Guard regulations dictate that all fluid relief devices are to be set at a maximum of 125 psi., viz. the prescribed safe working pressure of conventional transfer hoses employed in such operations. For safety reasons, liquid transfer aboard barges is generally accomplished in the 50 psi or less range. Transfer hoses are hydraulically tested at 11/2.times.maximum allowable pressure which normally equals about 187.5 psi. Such hoses are tested while positioned in a straight line, however, the strength of the hose is greatly reduced while in use where it becomes twisted, subjected to short radius bends, pinched, kinked, or similarly abused.
Many relief valves now in use aboard oil vessels are highly vulnerable to freezing by corrosion and once they become inoperative and should the flow be restricted due to human error with conventional line valves or other causes, the transfer hose becomes a relief valve. A burst oil transfer hose during operation can be economically and ecologically disasterous or cause an explosion or fire resulting in injury or death.